A typical freight train includes one or more locomotives, a plurality of railcars and a pneumatic trainline referred to as the brake pipe. The brake pipe consists of a series of individual pipe lengths interconnected to each other. One pipe length secured to the underside of each railcar interconnects to another such pipe length via a flexible coupling situated between each railcar. The brake pipe supplies the pressurized air that is required by the brake control system to charge the various reservoirs and operate the air brake equipment on each railcar in the freight train.
FIG. 1 illustrates a schematic diagram of a pneumatic brake control system of a railcar of a freight train. The brake equipment on each railcar typically includes one or more brake cylinders, an auxiliary air reservoir, an emergency air reservoir and a conventional pneumatic brake control valve such as an ABDX, ABDW or similar type control valve. The ABDX and ABDW pneumatic brake control valves are made by the Westinghouse Air Brake Company (WABCO) and are well known in the brake control art.
FIG. 1a illustrates a schematic diagram of a typical pneumatic brake control valve. This control valve includes a service portion and an emergency portion mounted on opposite sides of a pipe bracket. It should be noted that there exists at least one other type of pipe bracket on which the service and emergency portions are mounted on the same side. Whether dealing with the dual sided or single sided variety, the pipe bracket features a number of internal passageways and several ports. Each port connects to one of the interconnecting pipes from the railcar such as those leading to the brake pipe, the brake cylinder, the emergency reservoir and the auxiliary reservoir. It is through these ports and internal passageways of the pipe bracket that the relevant portions of the brake control valve communicate fluidly with the pneumatic piping on the railcar.
The service and emergency portions of the pneumatic brake control valve operate according to principles well known in the railroad industry. The service portion of the control valve performs several functions including (1) controlling the flow of air from the auxiliary reservoir to the brake cylinders during a service brake application, (2) controlling the recharging of the auxiliary and emergency reservoirs, (3) controlling the exhausting of the brake cylinders when the brakes are released; and (4) reinforcing the brake application and release signals pneumatically conveyed via the brake pipe. The emergency portion controls, among other things, (1) recognition of the emergency brake application signal pneumatically conveyed by the brake pipe and (2) the flow of air from both reservoirs to the brake cylinders during the emergency brake application. The emergency portion on each railcar also serves to propagate the emergency application signal along the train by rapidly venting the brake pipe to atmosphere.
The Association of American Railroads (A.A.R.) has issued specification S-486-91 detailing the basic test procedures that must be performed periodically on the brake equipment of every railcar. It requires that the brake equipment be charged and tested for leaks. There exists a standard A.A.R. test device that can be used to perform such testing, but it is rather complicated and requires interpretation by a very skilled user to identify problems with the brake equipment. Accordingly, in U.S. application Ser. No. 08/365,815, WABCO has described and claimed an Automated Single Car Tester that can perform the requisite tests more reliably and quickly than the standard A.A.R. test device. This copending application is assigned to the assignee of the present invention, and its teachings are incorporated into this document by reference.
Among other functions, the Automated Single Car Tester is used to measure the pressure at various points within the brake control system of the railcar. The single sided pipe bracket has a receiver assembly mounted to same side of the pipe bracket to which the service and emergency portions of the control valve mount. This receiver assembly provides the Automated Single Car Tester with quick and direct access to certain internal passageways of the pipe bracket and ultimately to the pneumatic pipes and reservoirs whose pressure must be tested. Specifically, through the receiver assembly, the Automated Single Car Tester can access and measure the pressures within the brake cylinder, the brake pipe, the emergency reservoir and the auxiliary reservoir. The dual sided pipe bracket, however, does not have integral access ports to which a receiver assembly can be mounted. Consequently, it is quite difficult to access the ports and the pipes that connect to them. Therefore, for railcars equipped with the dual sided pipe bracket, the Automated Single Car Tester is used in conjunction with a combination access plate and receiver assembly. The access plate portion of the assembly is interposed between the pipe bracket and the service portion of the control valve, as shown in FIGS. 1a and 1b. The receiver portion is assembled as shown in FIG. 1d. Connected to form the combined assembly as shown in FIG. 1b, the receiver portion together with the access plate provide access to the internal passageways of the pipe bracket. For railcars equipped with the dual sided pipe bracket, the combined assembly is the part through which the Automated Single Car Tester can access and measure the pressures within the brake cylinder, brake pipe, emergency reservoir and auxiliary reservoir.
As will be apparent from the ensuing description and claims, the receiver portion and the receiver assembly of the two aforementioned pipe brackets are identical except in respects immaterial to the present invention. Therefore, the terms "receiver assembly" and "receiver portion" shall hereinafter be used interchangeably.
As shown in FIG. 1d, the receiver assembly includes a cover, a receiver body and four check valves housed in bores defined in the receiver body. Each check valve basically includes a shaped insert made of rubber or other suitable sealing material, a carrier that holds the shaped insert and a spring. A gasket and typically a filter are also used with each check valve. Consequently, each check valve is normally compressed against a check valve seat formed at the top of its bore. When the receiver assembly is mounted to the control valve, the check valves, at the head of the receiver body, are accessible by removal of the cover. Each check valve serves as an access port through which to access the pressure held in one of the following devices: the brake cylinder, the brake pipe and the emergency and auxiliary reservoirs. Even with the cover removed, each check valve acts as a seal that prevents leakage of the air under pressure. When attached, the cover provides a seal redundant to that provided by each of the check valves to minimize the chance of leakage.
The Automated Single Car Tester includes an automatic test connector designed to mate with the head of the receiver body and thereby to each of the four access ports. The automatic test connector is operated by the tester so that each of the check valves may be moved automatically away from its check valve seat. In this manner, the Automated Single Car Tester can automatically charge, exhaust and measure the pressures in the brake cylinder, the brake pipe, the emergency reservoir and/or auxiliary reservoir.
For railcars in the field or in maintenance areas where an Automated Single Car Tester may not be available, manual testers are used to perform a limited test of the railcar brake equipment. The only existing manual tester connects to the brake pipe at one end of the railcar. During manual testing, it would be advisable to access the four primary pressures for the purpose of assisting with the aforementioned test procedures and/or measuring such pressures. In this case, a manual tester would be used to provide access to the various ports or passageways through which these critical pressures are to be measured. The prior art manual test connector features manually operated crankshaft valve lifters to provide access to the pressure to be measured. The disadvantage of such manual test connectors, however, is that they are rather large in size and are typically quite difficult to manufacture.
The foregoing background information is provided to assist the reader in understanding the invention described and claimed below. Accordingly, any terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.